Field of the Invention
The present invention relates to an apparatus and a method for transmitting wireless power, and more particularly, to an apparatus and a method for transmitting wireless power that rapidly and precisely adjusts impedance so as to transmit desired power.
Discussion of the Related Art
A wireless power transmission technology is a technology that wirelessly transmits power between a power source and an electronic apparatus. As one example, the wireless power transmission technology can wirelessly charge a battery of a mobile terminal just by putting a mobile terminal such as a smart phone or a tablet on a wireless charging pad to provide higher mobility, convenience, and safety than a wired charging environment using the existing wired charging connector. Further, the wireless power transmission technology attracts public attention to substitute the existing wired power transmission environment in various fields such as medical treatment, leisure, a robot, and the like, which include home appliances and an electric vehicle afterwards in addition to wireless charging of the mobile terminal.
The wireless power transmission technology may be classified into a technology using electromagnetic wave radiation and a technology using an electromagnetic induction phenomenon, and since the technology using the electromagnetic wave radiation has a limit of efficiency depending on radiation loss consumed in the air, the technology using the electromagnetic induction phenomenon has been primarily researched in recent years.
The wireless power transmission technology using the electromagnetic induction phenomenon is generally classified into an inductive coupling scheme and a resonant magnetic coupling scheme.
The electromagnetic inductive coupling scheme is a scheme that transmits energy by using current induced to a coil at a receiving side due to a magnetic field generated at a coil at a transmitting side according to electromagnetic coupling between the coil at the transmitting side and the coil at the receiving side. The wireless power transmission technology of the electromagnetic inductive coupling scheme has an advantage that transmission efficiency is high, but has a disadvantage that a power transmission distance is limited to several mms and is very sensitive to matching of the coils, and as a result, a degree of positional freedom is remarkably low.
The resonant magnetic coupling scheme as a technology proposed by Professor Marine Solarbeach of MIT in 2005 is a scheme that transmits energy by using a phenomenon in which the magnetic field concentrates on both sides of the transmitting side and the receiving side by the magnetic field applied at a resonance frequency between the coil at the transmitting side and the coil at the receiving side. As a result, the resonant magnetic coupling scheme is expected as the wireless power transmission technology that can transmit energy up to a comparatively long distance from several cms to several ms as compared with the magnetic inductive coupling scheme to implement authentic cord-free.
However, when wireless power transmission is performed, impedances at the transmitting side and the receiving side may vary depending on a transmission distance or state changes at the transmitting side and the receiving side. In this case, in general, matching the impedance by detecting a reflection wave has a problem that it is difficult to match the impedance rapidly and precisely because a response speed is low and a range of matching the impedance is small.